Fabrication processes of integrated circuits typically involve various stages for depositing thin films of various materials on the surface of a semiconductor substrate. The preparation of such thin films typically includes such methods as evaporation, chemical vapor deposition (CVD) such as plasma enhanced chemical vapor deposition (PEVCD), sputtering, and spin casting. The above deposition schemes are conventionally used as appropriate to deposit metals, silicon, polysilicon, and dielectrics such as silicon dioxide and silicon nitride on the substrate. Typical PEVCD precursors include DMDMOS (dimethyldimethoxysilane), or TOMCATS (tetramethylcyclotetrasiloxane). PEVCD tends to be limited, however, in allowing engineering latitude with respect to resulting film characteristics and types of precursor materials.
Alternatively, thin films may be deposited using a spin-on ultra low-k dielectric material, such as LKD-5109, a methylsilsesquioxane (MSQ) material manufactured by the JSR Corporation. Although high yields are possible using an ultralow-k material, in some cases it has been necessary to use thicker passivation and an additional oxide layer on top of the structure to deliver a more mechanically stable stack, in this way driving up fabrication complexity and cost, and further leading to a deterioration of the dielectric constant of the resulting film stack by virtue of the additional oxide layer. Moreover, similar to PEVCD, the spin-on technique allows limited resulting characteristics (e.g. toughness).
Electrospray (ES) ionization, a CVD technology in which a conductive liquid is volatilized in transit to the growth front, is also known as a method for depositing molecules onto relevant surfaces. The deposition of pure complex molecules on semiconductor surfaces under ultra high vacuum conditions using ES to allow an exploration of the interaction of the deposited molecules with the surface and with each other is also known. ES is typically used as an ionization technique for mass spectrometry, especially for the analysis of compounds of biological significance. ES has also been used for the deposition of protein thin films, for the deposition of ceramic thin films, and for the deposition of ferroelectrics. ES has also been disclosed along with a pretreatment of a substrate with radio frequency (RF) plasma.